The present invention relates to an improved liquid level controller. The control of liquid levels in vessels has long been accomplished through use of a float whose motion or buoyancy force is transmitted to a pneumatic or electric controller which is connected to a valve for opening and closing flow of liquid from the vessel. Examples of an early non-bleeding pneumatic controller of this type are shown in the A. S. Parks, U.S. Pat. Nos. 2,649,771; 3,052,254; 3,064,474; 3,120,241 and 3,128,784.
The C. E. Mason, U.S. Pat. No. 2,616,440 discloses a pneumatic liquid level controller which utilizes an arm connecting a float within the vessel to a torque tube which is secured to the back of the controller housing and to the controller mechanism. This patent illustrates a motion balance, constant bleed type of pilot. Another patent which also discloses a motion balance and constant bleed type of pilot is the A. J. Hanssen, U.S. Pat. No. 3,088,485. Both of theses units require right or left hand mounting when used as a liquid level controller. All of these devices include a means to vary sensitivity (proportional band).
The G. Ho. U.S Pat. No. 4,543,973 discloses a liquid level controller having a front pilot mounting but utilizes motion balancing and constant bleed type of pneumatic pilot nozzle. A similar device is didclosed in the C. Glasgow et al, U.S. Pat. No. 4,542,765. Liquid Level Lectronics, Inc. (LLC, Inc.) has marketed a front pilot mounting liquid level controlling but such device does not provide for a variable proportional band mechanism. The Ho, Glasgow et al and LLC, Inc. devices all have non-adjustable fixed proportional bands.
Most of the prior art liquid level controllers have included the right or the left hand mounting which requires that both mountings be available in inventory since their conversion between such mountings necessitates extensive reworking of the housing, the mounting and the components.